1. Field of the Invention
The present invention relates to a method and apparatus for forming a deposition film, particularly to a method and apparatus for forming a thin film to be used for a laminated thin film element such as a photovoltaic element on a substrate.
2. Description of the Related Art
For continuously forming deposition films to be used for a photovoltaic element and the like on a substrate, independent deposition chambers for forming each semiconductor layer have been provided to deposit each semiconductor layer in respective deposition chambers. For example, U.S. Pat. No. 4,400,409 discloses in its specification a continuous plasma CVD apparatus using a roll-to-roll method. This apparatus comprises plural glow discharge areas in which a sufficiently long and flexible substrate having a desired width is disposed along a passageway on which the substrate sequentially penetrates each glow discharge area. Using this apparatus, elements having semiconductor joints can be continuously formed by continuously conveying the substrate along its longitudinal direction while depositing a semiconductor layer of a desired conduction type in each glow discharge area. According to the specification described above, a gas gate is used for preventing diffusion and mingling of a dopant gas used for depositing each semiconductor layer into the other glow discharge areas. Practically, the glow discharge areas are isolated with each other using slits of separation passageways, and a flow of a sweeping gas such as Ar and H2 is created in this separation passageway.
Japanese Patent Publication No. 4-32533 discloses, on the other hand, in its specification a method using a surface protection sheet for protecting the surface of a ribbon shaped substrate in the roll-to-roll apparatus.
An example of a sputtering apparatus is described below with reference to drawings.
FIG. 3 shows an example of the sputtering apparatus, in which a reel-off vacuum chamber 101, a film deposition vacuum chamber 201 and a reel-up vacuum chamber 301 are connected with each other with gas gates 151 and 152, and the chambers are evacuated with a vacuum pump (not shown) connected to evacuation ports 102, 202 and 302.
A ribbon shaped substrate 10 is wound on a reel-off bobbin 111, and is conveyed toward the film deposition vacuum chamber 201 with its convey direction changed by a convey roller 112 (the direction denoted by an arrow A in the drawing).
The ribbon shaped substrate 10 is heated to a prescribed film deposition temperature with a lamp heater 203 in the film deposition vacuum chamber 201, and films are deposited on the ribbon shaped substrate 10 in film deposition chambers 204 and 206 using various kinds of targets 205 and 207. The ribbon shaped substrate 10 is reeled up with a reel-up bobbin 311 in the reel-up vacuum chamber 301 with its convey direction changed by a convey roller 312. During this reel-up procedure, a surface protection sheet 313 for protecting the surface of the ribbon shaped substrate 10 is fed from a reel-off core 314 and is reeled up on the bobbin 311 together with the ribbon shaped substrate 10.
A sweeping gas flows through the gas gates 151 and 251 by means of gas feed pipes 152, 153, 252 and 253 to prevent the gases from being mixed in each vacuum camber. The surface protection sheet 313 is provided in order to protect the surface of the ribbon shaped substrate 10 when it is reeled up on the bobbin. A sheet made of any materials may be used so long as it exhibits desired functions. Examples of the surface protection sheet available include fibrous sheets of paper and cloth, resin sheets such as polyethylene, polyester, PET, polyimide and polyamide sheets, and a sheet manufactured by coating a metal on one or both faces thereof.
For further improving photovoltaic conversion efficiency as a photovoltaic element, it is necessary to improve characteristics of a semiconductor film that absorbs a light and converts it into electricity, as well as characteristics of a back reflector film provided for reflecting a light. While this back reflector film is manufactured using conventional sputtering apparatus, the film is desirably formed with high quality and uniformity with good reproducibility.
Accordingly, it is an object of the present invention to provide a method and apparatus for forming a deposition film with higher quality, better uniformity and better reproducibility as compared with the deposition films formed by the conventional methods and apparatus.
For solving the above problems, the present inventors have completed through intensive studies the present invention having the constructions as described below.
In one aspect, the preset invention provides a method for forming a deposition film on a substrate in a film deposition chamber, wherein a gas adsorptive member is placed in a space communicating with the film deposition chamber, and the deposition film is deposited while continuously feeding a released gas component generated from the gas adsorptive member into the space. Preferably, the released gas component is fed by reeling off the gas adsorptive member.
In another aspect, the present invention provides an apparatus for forming a deposition film on a substrate in a film deposition chamber, comprising a gas adsorptive member disposed in a space communicating with a film deposition chamber, and a device for continuously feeding a released gas component generated from the member in the space. The apparatus may comprise a mechanism for reeling up a ribbon shaped gas adsorptive member on the roller. Preferably, the released gas component is continuously fed into the film deposition chamber.
In a different aspect, the present invention provides a method for treating a substrate comprising the steps of reeling off a rolled substrate in a first vacuum chamber, treating the substrate, and reeling up the substrate on a roll in a second vacuum chamber, wherein a rolled surface protection sheet is placed in the second vacuum chamber to reel up the sheet on the same axis as the axis of the rolled substrate while reeling off the sheet to release the gases from the surface of the sheet.
Further objects, featured and advantages of the present invention will become apparent from the following descriptions of the preferred embodiments with reference to the attached drawings.